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Author Topic: Setting up my first Beverage, looking for input  (Read 9500 times)

Offline Beam Tetrode

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Re: Setting up my first Beverage, looking for input
« Reply #15 on: September 29, 2010, 0503 UTC »
So the Beverage is up, about 1 Meter above ground and 80 Meters Long.
Even at that short a length it is working wonderfully ;D.  On 160 and 80 meters
signals are around S2 quieter then my G5RV at 40 Feet, but they are much easier
to hear as the antenna is much quieter. 
On the funny bands it works just like Tube Shortwave said, in fact I have not been able
to hear anything above 5 megs on it aside from local CW :-\.

I had never really considered a Loop or a Rhombic, but I have been convinced.
I've decided on a terminated Rhombic as my next antenna project.

I'll keep you all informed, and thanks again for all the tips and information.





Offline SW-J

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Re: Setting up my first Beverage, looking for input
« Reply #16 on: September 29, 2010, 1905 UTC »

On the funny bands it works just like Tube Shortwave said, in fact I have not been able
to hear anything above 5 megs on it aside from local CW :-\.



So ... numerical result data wasn't convincing?

  (copied from the first response - data from chart on W8JI website at the link found in the first post)

  http://www.w8ji.com/receiving.htm  )

Antenna Type        RDF  (dB)      20-degree forward gain (dBi)   
---------------    -----------     ----------------------------     
1/2wl Beverage           4.52                 -20.28           

Vertical Omni, 60
   1/4wl radials           5.05                     1.9


Gee, willya look at the "forward gain" at the 20 degree incoming angle ... much signal at 20 dB down *?  :) :) :)

Prior to seeing W8JI's chart I had not realized such a big difference existed (btw a beverage and 'sensitivity' related to elevation angle), and tend to be 'skeptical' of off-handed claims unless I can see some numerical data since there are so many old-wives -er- ham tales out there ...


Nice to see some confirmation of what W8JI saw too  :) :)


* Relative to a 0 or 1 degree elevation angle

o Icom IC-756ProII, ProIII, Alinco DX-70, Kenwood TS-680s
o WinRadio G303e, Degen/Kaito 1103/DE1103, Stoddart NM-25
o 1/2 wave 80m Dipole used with several tuners
o Tuned loops from 2' thru 16' diam. capable of 160m thru 10m

Offline Beam Tetrode

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Re: Setting up my first Beverage, looking for input
« Reply #17 on: September 30, 2010, 0623 UTC »
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So ... numerical result data wasn't convincing?

Sorry SW-J, nothing personal against you old bean, I just cant bring myself to trust numbers.
You see, they killed my father...

Offline syfr

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Re: Setting up my first Beverage, looking for input
« Reply #18 on: October 01, 2010, 0013 UTC »
Do you detect any significant directivity?

I could use a good antenna for the 4Mhz desert beacons and have the land... depending on the oriientation
Kiwsdr x 2. TenTec Paragon/NRD535

Offline Beam Tetrode

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Re: Setting up my first Beverage, looking for input
« Reply #19 on: October 01, 2010, 0659 UTC »
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Do you detect any significant directivity?

Yes, there is significant directivity with proper termination.
I used a potentiometer for my terminating resistor because I have no way of
measuring the feed point impedance. The get the proper setting I did the following.
On 80 meters I found a Ham behind me in Alaska talking to someone in the lower 48.
I hooked the output from my rig into a CB, walked down to the end of the beverage,
tuned in the CB on a handheld and then I adjusted the termination resistance to whatever
made the Alaskan's signal fade the most.

Interesting note, the Zo of my Beverage is around 800 Ohms.
Does that seem high?

Offline Token

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Re: Setting up my first Beverage, looking for input
« Reply #20 on: October 01, 2010, 1708 UTC »

On the funny bands it works just like Tube Shortwave said, in fact I have not been able
to hear anything above 5 megs on it aside from local CW :-\.



So ... numerical result data wasn't convincing?

  (copied from the first response - data from chart on W8JI website at the link found in the first post)

  http://www.w8ji.com/receiving.htm  )

Antenna Type        RDF  (dB)      20-degree forward gain (dBi)   
---------------    -----------     ----------------------------     
1/2wl Beverage           4.52                 -20.28           

Vertical Omni, 60
   1/4wl radials           5.05                     1.9


Gee, willya look at the "forward gain" at the 20 degree incoming angle ... much signal at 20 dB down *?  :) :) :)

Prior to seeing W8JI's chart I had not realized such a big difference existed (btw a beverage and 'sensitivity' related to elevation angle), and tend to be 'skeptical' of off-handed claims unless I can see some numerical data since there are so many old-wives -er- ham tales out there ...


Nice to see some confirmation of what W8JI saw too  :) :)


* Relative to a 0 or 1 degree elevation angle



A couple of issues here.

The W8JI data quoted does not really explain why Beam Tetrode is not getting better performance, and, a pet peeve of mine, when is a Beverage a Beverage?

First, the W8JI data does not explain why Beam Tetrode is not getting the performance he should from the Beverage.  The quoted numbers, for a half wave Beverage, are not applicable to the areas he is having problems with.

Beam Tetrode has a Beverage that is 80 meters long.  He specifically states it works with better signal to noise than his G5RV on 160 and 80 meters but is not working well above 5 MHz.  At 5 MHz the antenna is near 2 wavelengths and the 20 degree gain performance from the W8JI chart should be within 6 dB of the vertical.  6 dB is 1 or 2 S units, depending on how your radio is calibrated.  1 or 2 S units are important, don’t get me wrong, but should not equal “I have not been able to hear anything above 5 megs on it aside from local CW”.

The next section is a minor rant from me, feel free to ignore it, but I am agonna say it ;)  A half wave Beverage just is not a Beverage, I tell ya!  By the way, it is presented here for discussions sake, not arguments sake, if it comes off confrontational that is accidental.

What makes a Beverage a Beverage?  The original patent (1381089, filed June 7 1921) claims that the operational affects of the Beverage start at “over” 1/2 wavelength and increases in performance from that point.  More recent definitions of the length of a Beverage (and all known real-world applications of the Beverage by it’s inventor, Harold Beverage) are “more than one wavelength”.  While this does not mean a Beverage or Beverage like antenna cannot be only half a wavelength it would be a strong indicator that if you want one to work, as a Beverage instead of as a random low wire, they should be “long” in relationship to the wavelength, ie, a full wave or longer.

With this in mind it becomes pretty clear why the W8JI data shows such a high main lobe for a 1/2 WL “Beverage”.  A 1/2 wave antenna that is unterminated will display a main lobe somewhat perpendicular to the wire axis in free space.  In close proximity to the ground the primary lobe energy towards the ground will be reflected up, adding to and remaining in plane with the perpendicular to wire axis lobe, OK, it can become somewhat more pronouncedly double lobed at this point.  Terminating the wire at the far end will “bend” the lobe towards the termination.  The velocity of the signal in the conductor is slower than the velocity of the signal in free space, so the longer the wire, the more the lobe will be “bent” towards the termination end.

So, a halfwave Beverage will have a high angle cone in the direction of the termination.  The longer the length of the Beverage the lower the included angle of this cone, and the greater the gain in the primary lobe.  At a half wave the main beam is pointed up so the gain towards the horizon, relative to a “no gain” (some verticals do have gain, lets assume none for this) omni directional vertical, is down significantly, just over 20 dB if the W8JI data is correct (and there is no reason to believe it is not).  The main lobe itself of the Beverage may have more gain than the vertical (probably around 3 dB if the vertical is 1/4 wave), but it is pointed more up in relationship to the vertical.

As I said above, the longer the Beverage the more this main lobe comes down towards the horizon and, at the same time, the more gain the main lobe has.  And thus the gain delta at 20 degrees between the vertical and Beverage is down to about –6 dB by the time the Beverage is 2 wavelengths long.  However, the gain in the main lobe is now up around +4 dBi or more.  So, the longer the better, but also the more directional.

But all of this is plotted along the wire axis.  The main lobe at the horizon and some angle (angle depends on antenna length and other factors) off the axis of the wire in the horizontal plane will be many dB up from the vertical omni performance.  These main lobes on the horizon still will not have as much gain as the main lobe up does, but it is closer to the theoretical.

Placement of a Beverage, or any other fixed directional antenna, is important because once placed they are going to work well in a specific direction and, by design, not so well in others.  With a Beverage think about where you are placing the lobes, not just the wire axis, a long enough Beverage (say over 3 Lambda) should start to blur the lobes with the wire axis.  With a Rhombic the central axis is the lobe axis.
T!
Mojave Desert, California USA

Offline Token

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Re: Setting up my first Beverage, looking for input
« Reply #21 on: October 01, 2010, 1802 UTC »

I put two and two together and deduced from his location ('Yukon wilderness') and his inclination towards a beverage that he might be desiring some directionality and gain back into the states ... the original suggestion towards a loop was made before Beam revealed he had 'nice big property'  :) :) so ... he could build something with some nice gain *and* directionality too, sounds like a prescription written for a Rhombic!

Token, Beam's original query was about construction details, poles/suppots (peg legs  :) :) ) and such - what did you use to hoist/hold your Rhombics up?


Yep, I missed the post he made about location and did not see a need for directionality, I do see it now and agree.

My Rhombics are pretty simple, and light duty.  Around here we have high winds, but nothing like ice loading to worry about.  Because of the high winds I keep my antennas a bit lower than is optimal and accept the performance hit for the ease of maintenance and lower install cost.

Each of my three Rhombics are built slightly differently from the others, but the basics are all the same.

Each are supported by 4 metal poles, one at each of the four points of the “diamond”, feedpoint end, termination end, and across the middle.  If I was going higher or was building a bit more heavy duty I would use telephone poles.  Each antenna is about 30 feet above the ground.  As I said before two are 450 feet along the long axis and 190 feet across the width, one is 300 feet along the long axis and about 130 feet in width (I don’t have the exact width handy).

At the feed end the antenna the balun is mounted directly to the pole and the pole is hinged at the base so that I can lay it over to work on the feed point.  Each of the other three support points use a pulley mounted to the top of the pole, and nylon rope through the pulley so that I can lower the antenna to the ground for work.  The apex points across the middle are simple antenna insulators and the wire is allowed to float in the insulator.  I have even used ¾ inch sched 40 PVC pipe to make these insulators in the past.  At the termination end is a plexiglass plate with eye bolts to accept the antenna wire, and (on 2 antennas) an 600 Watt 800 Ohm non-inductive load, that is slight overkill, mounted on the plate.  A 600 Watt termination means I can key down 1200 Watts CW indefinitely, and legal limit for extended periods.  In reality a 300 Watt termination should be able to handle legal limit transmissions on SSB with reasonable duty cycles.  The third antenna has only a 200 Watt term resistor, it has handled legal limit power, but I try to remember to not push that antenna as hard.  Included on the plate is a relay so that I can select the termination or deselect it.  With the termination selected the antenna is monodirectional, lower noise, and broader banded.  With the termination deselected the antenna is biderectional, but much more peaky in performance as it becomes more resonance limited.

The feedline is 50 Ohm coax, either LMR400 or RG-214, depending on which antenna.  I have tried both 9:1 and 16:1 baluns, I saw little receive performance difference between them and I think all three are currently using 9:1.  For transmit use I use a tuner at all times, but the raw SWR is not too bad in several bands.

The wire used is not all that important, unless you are running high power, and for receive or lower power (say 400 W or less) transmit applications I have run #18 stranded copper ground wire that can be gotten at places like Home Depot for about $30 for 500 feet.

If you have the land and can orient a Rhombic in a “good” reception direction for you then a Rhombic is a decent choice.  But, if you are unsure of your primary reception directions, or want omni performance, than a large sky loop would be my selection.
T!
Mojave Desert, California USA

Offline Beam Tetrode

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Re: Setting up my first Beverage, looking for input
« Reply #22 on: October 03, 2010, 0644 UTC »
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A half wave Beverage just is not a Beverage

Agreed, I cut my Bevy to be 2λ at 6.925 (86.6 meters to be exact).
I was on the ball in that regard, however comically futile my precision was.

Offline John Poet

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Re: Setting up my first Beverage, looking for input
« Reply #23 on: October 03, 2010, 0957 UTC »
Less ice, more liquor.

That's my advice and I'm sticking to it

 :D

John Poet

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Re: Setting up my first Beverage, looking for input
« Reply #24 on: October 03, 2010, 2244 UTC »
Less ice, more liquor.

That's my advice and I'm sticking to it

 :D

I was dying to say something similar this whole thread.

Thank you! ;D

Peace!

Offline Beam Tetrode

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Re: Setting up my first Beverage, looking for input
« Reply #25 on: October 04, 2010, 0736 UTC »
It took me entirely to long to realize what you were talking about.

 

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